Change of Base

Formula

log_ab = (log_cb) / (log_ca)

Useful when your calculator only has log₁₀ (log) or ln (log_e).

Examples

log₂10 = log 10 / log 2 ≈ 1 / 0.3010 = 3.32

log₅20 = log 20 / log 5 ≈ 1.3010 / 0.6990 = 1.86

Note: You can use any new base c, but base 10 or e is easiest.

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